Apex domains cannot have CNAME records.
Question and response
Question
dig cert.ee. NS
Answer
cert.ee. 4 NS e.tld.ee.
cert.ee. 4 NS ns.cert.ee.
cert.ee. 4 NS sec1.rcode0.net.
cert.ee. 4 NS pch.cert.ee.
cert.ee. 4 NS ns2.cert.ee.
cert.ee. 4 NS sec2.rcode0.net.
Authority
The response has no authority records.
Additional
ns.cert.ee. 4 A 195.80.103.60
ns2.cert.ee. 4 A 46.226.136.4
pch.cert.ee. 4 A 204.61.216.142
sec1.rcode0.net. 3 A 192.174.68.100
sec2.rcode0.net. 3 A 176.97.158.100
ns.cert.ee. 4 AAAA 2a02:88:1:e:300:0:0:60
ns2.cert.ee. 4 AAAA 2a00:6a00:ad1:136:0:0:0:4
pch.cert.ee. 4 AAAA 2001:500:14:6142:ad:0:0:1
sec1.rcode0.net. 3 AAAA 2001:67c:1bc:0:0:0:0:100
sec2.rcode0.net. 3 AAAA 2001:67c:10b8:0:0:0:0:100
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0